The fuel injection pump assembly on the current diesel water pump is usually a whole assembled by components such as a fuel injection pump and a governor. Among them, the governor is a component that guarantees the low speed operation of the diesel engine and the limit of the maximum speed, and ensures a certain relationship between the injection quantity and the rotation speed. The fuel injection pump is the most important component of the diesel engine. It is regarded as the "heart" component of the diesel engine. If it goes wrong, the whole diesel engine will malfunction. Only the fuel injection pump will be described in detail below.
There are three types of fuel injection pumps: in-line, distributed, and single-type. Regardless of the type, the key to the fuel injection pump is a “pump”. The amount, pressure and time of the pump oil are very precise and are automatically adjusted to the load. The fuel injection pump is a component with fine processing and complicated manufacturing process. At present, the fuel injection pumps of general automobile diesel engines at home and abroad are produced by a few professional factories in the world.
Take the in-line fuel injection pump as an example to see how the “pump” works:
The fuel injection pump must have a power source to operate, and the lower camshaft is driven by the engine crankshaft gear.
* The key part of the fuel injection pump is the plunger. If the analogy of the common syringe in the hospital is used, the movable stopper is called the plunger, and the syringe is called the plunger sleeve. It is assumed that a spring is placed inside the needle. One end of the plunger and the other end of the plunger contact the camshaft. When the camshaft rotates one revolution, the plunger will move up and down within the plunger sleeve. This is the basic movement of the plunger of the fuel injection pump.
* The plunger and plunger sleeve are very precise fittings. The plunger body has an inclined groove, and the plunger sleeve has a small hole called a suction port. The suction port is filled with diesel oil. When the plunger inclined groove faces the suction port, the diesel oil enters the plunger sleeve, and the plunger is camshaft. When the top is at a certain height, the inclined groove of the plunger is staggered from the suction port, and the suction port is closed, so that the diesel can neither be inhaled nor pressed out. When the plunger continues to rise, the diesel oil is pressed, and the diesel pressure is pushed to a certain extent. The valve swarms out into the injector and then enters the cylinder combustion chamber from the injector.
* It is important to point out here that the diesel engine has an inlet pipe and a return pipe. The inlet pipe is easy to understand, so what is the use of the return pipe? The original plunger discharges a certain amount of diesel oil each time, only a part of it is injected into the cylinder, and the rest is vented by the oil return hole, and the amount of oil injected is adjusted by increasing or decreasing the amount of oil discharged.
* When the plunger moves up to the "upper point" and moves down, the plunger tilting groove of the diesel water pump will meet the suction port again, and the diesel oil is sucked into the plunger sleeve again, repeating the above action again. In-line fuel injection pump each group of plunger system corresponds to one cylinder, 4 cylinders have 4 sets of plunger system, so the volume is relatively large, mostly used in medium-sized cars. For example, diesel engines on buses and large trucks generally use in-line fuel injection pumps.
Fuel injection pumps on cars and light-duty diesel engines are generally distributed, with the advantages of small size, light weight, and simple structure. It is pressurized with two sets of plunger systems (or a set of plunger systems) that are fed separately to each injector.
Its basic working principle is that there are two sets of opposed plungers installed on the impeller in the pump. When the impeller is rotated by the engine, the plunger also rotates. Because the convex part of the cam ring presses the plunger, the plunger is made. The diesel oil is pumped to the oil feed hole in the center of the impeller as the pump acts. At this time, the diesel fuel is filled at the inlet of the distributor, and then the injection is arranged in the order of each cylinder.
Since the number of revolutions of the two sets of plunger systems (or a set of plunger systems) increases in proportion to the number of cylinders, the fuel injection pump is limited by the number of cylinders and the maximum number of revolutions of the diesel engine.
With the development of diesel engine technology, a single type of fuel injection pump (called a single pump or a pump nozzle) has been developed, which actually "normalizes" the above two types of fuel injection pumps, each engine Each cylinder fuel injection is performed by a separate injection unit (single pump or pump nozzle).
For the single pump, the fuel injection pump and the fuel injection nozzle are connected by a short high-pressure oil pipe, and for the pump nozzle, the fuel injection pump and the fuel injection nozzle are integrated into one body and directly mounted on the cylinder head of the diesel engine. Driven by an overhead camshaft. Their greatest advantage is the ability to mitigate or eliminate the effects of pressure waves in the high pressure fuel line during diesel flow and injection. Because this pressure wave will hinder the fuel system from matching with load and speed, and will increase with the length of the high pressure pipe.